Apple Inc. unveiled the iPhone 5 in an overhaul aimed at widening its lead over Samsung Electronics Co. and Google Inc. in the $219.1 billion smartphone market.

I was wrong. Since the map flap, Apple's stock has not only slipped, but underperformed the S&P 500 and the Nasdaq composite.

Turns out Mapgate, while like a blip in Apple's history, stirred a much bigger conversation that points to vulnerabilities and concerns every Apple investor should, in the least, ponder: Apple may finally have just struck that point that all fast-growing companies hit—where its phones and operating system are so good they can't really technologically leapfrog themselves in a meaningful way.

When that happens, as Apple just learned (and Microsoft, years earlier), customers are unwilling to accept inferior function over form; it's almost like a violation of an intangible trust.

All of that smacks of a rapidly maturing smartphone market, in which price eventually starts to matter, raising questions about a vulnerability not yet seen: The prospect that Apple could lose pricing power, especially its ability to wring out a premium subsidy from wireless carriers like Verizon and AT&T ? Right now, carriers subsidize more than half the cost of an iPhone.

"People realize there is only so much you can do to incrementally make improvements," says Walter Piecyk, the BTIG analyst and longtime Apple bull who caused a stir last April when he had the nerve to downgrade Apple. As a result, he told me yesterday, "the phones are technologically closer than they used to be."

The real line in the sand, many watchers believe, is if and when Verizon says it won't pay a premium subsidy for the iPhone.

Piecyk warned of as as much in his April downgrade, when he wrote:

Wireless operators have been happy to subsidize smartphones to new and existing customers in order to provide a lift to the average monthly bill of their customer base, a metric which had been falling for the past three decades.

But that happened at the expense of their own profitability. Verizon recently started trying to counter the cost of subsidies (and perhaps providing a preview of what may come next) by taking it out of the hide of customers by shifting to a-la carte data plans and a $30 upgrade fee on discounted smartphones.

The next step, a growing chorus of watchers believe, will come at the expense of phone makers, starting with the premium subsidy Apple gets for the iPhone.

And if that happens, will Apple be forced to lower the price of the iPhone? Or will it expect consumers to pay a bigger share? And if so, will they?

"From the carrier's perspective I think it's also important to remember that the total subsidy that they pay is fairly small relative to the monthly payments that they collect over a 24-month contract period," he said. "And I think many would tell you, they certainly told me, that iPhone has several advantages for them over other smartphones. The churn rates are much less. You see carriers now focusing on shared data plans and I think an iPhone customer is likely more—is more likely to have a tablet or an iPad, and so I think they really value these customers quite a bit."

And for Apple's sake, and the sake of investors counting on the stock to continue to move higher—and stay at new heights—they had better continue to do so.

Lost in the euphoria over Apple by many casual investors is this: For all of the talk about how the iPhones feed the Apple ecosystem, the iPhone drives Apple's sales and profits, generating roughly half of sales and, according to analysts, as much of two-thirds of operating profits, if not more.

In other words, as goes the pricing of the iPhone, so goes Apple.

Oh, and yes: The iPad mini is expected to be rolled out soon with a smaller screen and lower price. If nothing else it's expected lower price will be proof that Apple can't sustain a premium price in an increasingly competitive space.

Which gets to the moral of this story, and the one thing investors should never forget: As great as Apple may be, it's still merely mortal.

P.S.: When it comes to Apple's stock, the next six months could be critical. When its first quarter is reported in early January investors should get a better handle on how well the iPhone 5 did (or didn't.) The iPad mini will have been rolled out, and we'll see whether it generated considerably more new customers or cannibalized its existing base. And there should start to be chatter about the iPhone 5s, or an equivalent new model, and whether it has enough new technology to spark widespread customer interest, even among the fanboys.

Also keep an eye on talk about mid-level employee defections—another sign of a maturing company.

Finally, be leery of Apple splitting its stock. That would be an indication that the company is running low on its operating arsenal to keep its shares elevated. It doesn't mean Piper Jaffray's Gene Munster won't be right—and Apple's shares won't hit $1,000, on the next wave of iPhone 5 news. But if and when they do the ultimate question arises: Can they stay there?

You can't help but love the drama (unless, of course, you're an investor!)